1. Field of the Invention
This invention relates to a telemetric temperature device and, in particular, to a telemetric temperature probe for microwave processing, typically microwave cooking.
2. Description of the Prior Art
Microwave ovens are home appliances of increasing popularity and sales. The advantages offered by the microwave ovens include compactness and high thermal efficiencies and speed in cooking. The temperature of comestibles heated in the microwave ovens has not, heretofore, been precisely controlled because of a lack of precision in detection of temperatures of comestibles within microwave ovens. Temperature control is particularly difficult with small size comestibles since the highly efficient microwave oven heats small comestibles so rapidly that ordinary timed control of the heating process fails to provide reliable temperature control.
A number of attempts have been made to provide direct measurement of temperatures of comestibles within a microwave oven. Included in these attempts have been positioning of microwave absorbent material in an internal fixture of the oven and measuring the temperature of this material, thereby deriving a signal which is proportional to the total energy input to the oven. The difficulty with this approach is that the temperature reached by a comestible placed within the oven depends on its mass and condition and only a direct temperature measurement of the comestible is, therefore, reliable.
Another attempt has been made to provide a thermometer which can be inserted into the comestible. The thermometer is provided with a non-ionic temperature responsive fluid to avoid its interaction with the microwave energy. While this device can be used as a thermometer, it does not provide for automatic control of the microwave oven in response to the sensed temperatures.
Another attempt has been made in which a temperature responsive circuit is positioned within a probe which is coupled through an umbilical cord to the oven control circuit. The umbilical cord provides the power supply to the temperature responsive circuit and transmits the temperature responsive signal to the oven control circuit. This device is somewhat cumbersome, requiring that the probe be inserted and removed from the comestible or disconnected from the oven whenever the comestible is to be placed in or removed from the oven.